EP3813385A1 - Capteur à ultrasons - Google Patents

Capteur à ultrasons Download PDF

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Publication number
EP3813385A1
EP3813385A1 EP19826265.1A EP19826265A EP3813385A1 EP 3813385 A1 EP3813385 A1 EP 3813385A1 EP 19826265 A EP19826265 A EP 19826265A EP 3813385 A1 EP3813385 A1 EP 3813385A1
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EP
European Patent Office
Prior art keywords
matching layer
acoustic matching
ultrasonic sensor
adhesive
piezoelectric element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19826265.1A
Other languages
German (de)
English (en)
Other versions
EP3813385A4 (fr
Inventor
Masamichi Hashida
Tomoki Masuda
Masaki NOBUNAGA
Hidetomo Nagahara
Yudai Ishizaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Intellectual Property Management Co Ltd
Original Assignee
Panasonic Intellectual Property Management Co Ltd
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Filing date
Publication date
Application filed by Panasonic Intellectual Property Management Co Ltd filed Critical Panasonic Intellectual Property Management Co Ltd
Publication of EP3813385A1 publication Critical patent/EP3813385A1/fr
Publication of EP3813385A4 publication Critical patent/EP3813385A4/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
    • B06B1/067—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface which is used as, or combined with, an impedance matching layer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/28—Details, e.g. general constructional or apparatus details providing acoustic coupling, e.g. water
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2437—Piezoelectric probes
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones

Definitions

  • the present invention mainly relates to a sensor that transmits and receives ultrasonic waves.
  • piezoelectric elements are generally configured by ceramics (having high density and a high acoustic velocity), and the density and acoustic velocity of gas such as air to which the ultrasonic waves are transmitted are significantly smaller than those of ceramics.
  • the energy transfer efficiency from the piezoelectric element to the gas is significantly low.
  • measures have been taken to increase the energy transfer efficiency by interposing an acoustic matching layer having a smaller acoustic impedance than the piezoelectric element and a larger acoustic impedance than the gas between the piezoelectric element and the gas.
  • acoustic impedance Z2 of the acoustic matching layer needs to be significantly smaller than an acoustic impedance of a solid substance to approach acoustic impedance Z3 of gas.
  • a substance having a low acoustic impedance is a substance having a low acoustic velocity and a low density, and in many cases, is generally easily deformed. For these reasons, few substances satisfy properties required for the acoustic matching layer.
  • the acoustic impedance of the piezoelectric element including a solid substance and the acoustic impedance of gas are different by about 5 digits
  • the acoustic impedance of the acoustic matching layer needs to be reduced by about 3 digits of the acoustic impedance of the piezoelectric element in order to satisfy equation (1).
  • few substances satisfy the characteristics of the acoustic matching layer.
  • equation (1) is satisfied for the acoustic impedance of the piezoelectric element and a first layer (first acoustic matching layer), and the acoustic impedance of the first layer and the acoustic impedance of a second layer (second acoustic matching layer (object to which the ultrasonic waves are transmitted)), and the transmission efficiency is highest when equation (1) is satisfied between the acoustic impedance of the second layer and gas.
  • the first acoustic matching layer is desirably a hard material that reduces energy loss due to deformation (having a large elastic modulus), and in particular, a hard resin such as poly ether ether ketone (PEEK).
  • PEEK poly ether ether ketone
  • a through-hole in the acoustic matching layer is provided to prevent air bubbles from being mixed into a bonded surface during adhering (see, for example, PTL 2).
  • the piezoelectric element and the acoustic matching layer are bonded by a planar adhesive.
  • a periphery of the piezoelectric element is held by a cushioning member, there is a possibility that a stress due to the thermal expansion coefficient may increase at a part away from the cushioning member, that is, near a center of the piezoelectric element.
  • a candidate for a general acoustic matching layer having excellent properties is a resin having a large elastic modulus.
  • examples of the resin having a large elastic modulus include super engineering plastics such as PEEK, which also has poor adhesion.
  • the acoustic matching layer when a hard resin is used as the acoustic matching layer, there has been a possibility that the acoustic matching layer may be peeled off particularly near the center. Further, when the acoustic matching layer is provided with a through-hole having a diameter of a considerable degree or more, there has been a possibility that performance of the ultrasonic sensor may be reduced due to a reduction of ultrasonic waves.
  • An ultrasonic sensor of the present disclosure includes a piezoelectric element, a first acoustic matching layer adhered to the piezoelectric element, and an adhesive that adheres the first acoustic matching layer to the piezoelectric element, in which the first acoustic matching layer has a void having an opening on a surface adhered to the piezoelectric element, and the adhesive is filled in the void.
  • the ultrasonic sensor in the present disclosure can obtain an anchor effect and excellent durability by integrating the adhesive that solidifies in the void and the adhesive that adheres the piezoelectric element and the first acoustic matching layer.
  • the acoustic matching layer is adhered to the piezoelectric element or a metallic member bonded to the piezoelectric element to ensure electrical conductivity.
  • the piezoelectric element includes ceramics such as lead zirconate titanate.
  • the object to be adhered is a resin having poor adhesion and a ceramic or a metal that is relatively easily adhered.
  • the acoustic matching layer is provided with a void that communicates with the opening, and the adhesive that is cured after filling the void is bonded to the acoustic matching layer by chemical bonding and a mechanical bonding, that is, the anchor effect.
  • the adhesive that is cured after filling the void is bonded to the acoustic matching layer by chemical bonding and a mechanical bonding, that is, the anchor effect.
  • the piezoelectric element and the acoustic matching layer which are firmly bonded, are not easily peeled off even when stress due to a difference in the thermal expansion coefficient occurs, and the ultrasonic sensor having excellent durability can be provided.
  • the acoustic matching layer has an opening that opens to a bonded surface and a void that communicates with the opening.
  • the acoustic matching layer and the adhesive can obtain strong bonding by the anchor effect. Therefore, the acoustic matching layer, which includes a material having poor adhesion, can obtain strong bonding to the piezoelectric element.
  • Hard resin having excellent properties as an acoustic matching layer for example, super engineering plastic such as PEEK tends to have poor adhesion.
  • the hard resin can be used as an acoustic matching layer by firmly bonding to the piezoelectric element by the anchor effect. As described above, an ultrasonic sensor having excellent characteristics and reliability can be provided.
  • FIG. 1 is a schematic sectional view of an ultrasonic sensor according to a first exemplary embodiment.
  • ultrasonic sensor 1 includes piezoelectric element 2, adhesive 3, case 4, first acoustic matching layer 5, second acoustic matching layer 6, and electrodes 7a, 7b.
  • Case 4 is a bottomed tubular metal member. Piezoelectric element 2 is bonded to first surface 4b, which is an inner side of top surface 4a as a flat plate of case 4, with conductive adhesive 9. First acoustic matching layer 5 is bonded to second surface 4c, which is an outer side of top surface 4a of case 4, with adhesive 3 so as to face piezoelectric element 2. Furthermore, second acoustic matching layer 6 is bonded to a surface of first acoustic matching layer 5 not facing case 4 with adhesive 3. Further, electrode 7a is connected to electrode 2a of the piezoelectric element, and electrode 7b is connected to case 4.
  • Electrode 2b of the piezoelectric element is bonded to case 4 with conductive adhesive 9, and thus piezoelectric element 2 oscillates and emits ultrasonic waves by applying a predetermined voltage between electrodes 7a, 7b.
  • the emitted ultrasonic waves are eventually transmitted to a gas through case 4, first acoustic matching layer 5, and second acoustic matching layer 6.
  • Case 4 has a bottomed cylindrical shape, but may have a flat plate shape.
  • first acoustic matching layer 5 has a plurality of openings 8a on a surface facing case 4.
  • Voids 8 having a wedge shape or truncated cone shape and having a smallest sectional area parallel to a surface bonded to case 4 near openings 8a are provided continuously to openings 8a.
  • liquid adhesive 3 is filled in voids 8 in advance, and the surface having openings 8a of first acoustic matching layer 5 and second surface 4c of case 4 are bonded directly or via adhesive 3 coated therebetween while adhesive 3 filled in voids 8 is wet. Then, adhesive 3 is solidified to bond case 4 and first acoustic matching layer 5.
  • a characteristic required for ultrasonic sensor 1 is to propagate the ultrasonic waves generated at piezoelectric element 2 to a gas with high efficiency. It is therefore necessary to bond piezoelectric element 2, case 4, first acoustic matching layer 5, and second acoustic matching layer 6 while ensuring sufficient strength and environmental durability.
  • the members desirably have thermal expansion coefficients as similar as possible. This is to avoid a defect in an interface when a temperature change in the product in which members having different thermal expansion coefficients are bonded causes a shearing force due to a difference in the thermal expansion coefficients to act on the bonded interface.
  • Piezoelectric element 2 generally includes ceramics
  • case 4 generally includes metal. Ceramics and metal are both relatively easy to bond and relatively similar in thermal expansion coefficient, and thus piezoelectric element 2 and case 4 are relatively easy to bond.
  • First acoustic matching layer 5 includes a resin
  • second acoustic matching layer 6 also often includes a resin.
  • first acoustic matching layer 5 and second acoustic matching layer 6 have similar thermal expansion coefficients, and are relatively easy to bond.
  • case 4 often includes metal
  • first acoustic matching layer 5 often includes resin
  • the thermal expansion coefficients of case 4 and first acoustic matching layer 5 are generally greatly different.
  • the resin included in first acoustic matching layer 5 is highly likely to be PEEK or the like having poor adhesion, and may be peeled off from adhesive 3 on the interface.
  • an element required for propagating ultrasonic waves from piezoelectric element 2 to a gas with high efficiency is to securely bond adhesive 3 and first acoustic matching layer 5.
  • voids 8 having a wedge shape or truncated cone shape and having the smallest sectional area near openings 8a are provided, and the adhesive cured inside voids 8 cannot pass through openings 8a.
  • a strong anchor effect is obtained, which strengthens the bonding of adhesive 3 and first acoustic matching layer 5.
  • adhesive 3 and first acoustic matching layer 5 are not easily peeled off from each other even if the shearing force due to the difference in thermal expansion coefficients acts between adhesive 3 and first acoustic matching layer 5.
  • This configuration makes it possible to obtain excellent bonding from piezoelectric element 2 to the second acoustic matching layer and to provide an ultrasonic sensor having excellent durability against environment such as thermal shock.
  • a shape of voids 8 is a wedge shape or truncated cone shape.
  • voids 8 only have to partially have a sectional area larger than an opening sectional area of openings 8a.
  • ultrasonic sensor 1 has case 4 and second acoustic matching layer 6.
  • a configuration such as ultrasonic sensor 31 shown in FIG. 6A in which the second acoustic matching layer is not used, a configuration such as ultrasonic sensor 41 shown in FIG. 6B in which the case is not used, or a configuration such as ultrasonic sensor 51 shown in FIG. 6C in which neither the case nor the second acoustic matching layer is used can be implemented in various aspects without departing from the gist of the present disclosure.
  • FIG. 2 is a schematic sectional view of an ultrasonic sensor in a second exemplary embodiment.
  • FIG. 3 is a top view of a first acoustic matching layer shown in FIG. 2 , and a broken line shown in FIG. 3 indicates a position of the section in FIG. 2 .
  • ultrasonic sensor 11 includes piezoelectric element 2, adhesive 3, case 4, first acoustic matching layer 15, second acoustic matching layer 6, and electrodes 7a, 7b.
  • components denoted by the same reference marks as those in the first exemplary embodiment have the same configurations as components in the first exemplary embodiment, and the description thereof will be omitted.
  • a difference between ultrasonic sensor 11 according to the present exemplary embodiment and ultrasonic sensor 1 according to the first exemplary embodiment is a structure of first acoustic matching layer 15.
  • each of voids 18 in first acoustic matching layer 15 has a cylindrical shape, and is manufactured as a through-hole penetrating from the surface facing case 4 to the surface facing second acoustic matching layer 6 by injecting and molding a resin.
  • liquid adhesive 3 is filled in voids 18 in advance, and case 4, first acoustic matching layer 15, and second acoustic matching layer 6 are superposed while adhesive 3 is wet. Then, adhesive 3 is solidified to bond case 4, first acoustic matching layer 15, and second acoustic matching layer 6.
  • first acoustic matching layer 15 is joined via adhesive 3 filled in the through-holes as voids 18, and thus a strong anchoring effect is obtained, which strengthens bonding of adhesive 3 and first acoustic matching layer 15.
  • a defect can be avoided even if the shearing force due to the difference in thermal expansion coefficients acts between adhesive 3 and first acoustic matching layer 15.
  • This configuration makes it possible to obtain excellent bonding from piezoelectric element 2 to second acoustic matching layer 6 and to provide an ultrasonic sensor having excellent durability against environment such as thermal shock.
  • the above density makes it possible to easily establish equation (1) for piezoelectric element 2 and second acoustic matching layer 6, and to provide an ultrasonic sensor having excellent characteristics.
  • Voids 18 (through-holes) in first acoustic matching layer 15 may be manufactured by injecting and molding a resin, or the through-holes may be formed by machining a metal disc.
  • FIG. 4 is a schematic sectional view of an ultrasonic sensor according to a third exemplary embodiment
  • FIG. 5 is a top view of a first acoustic matching layer shown in FIG. 4 .
  • ultrasonic sensor 21 includes piezoelectric element 2, adhesive 3, case 4, first acoustic matching layer 25, second acoustic matching layer 6, and electrodes 7a, 7b.
  • piezoelectric element 2 adhesive 3, case 4, first acoustic matching layer 25, second acoustic matching layer 6, and electrodes 7a, 7b.
  • components denoted by the same reference marks as those in the first exemplary embodiment have the same configurations, and the description thereof will be omitted.
  • a difference between ultrasonic sensor 21 according to the present exemplary embodiment and ultrasonic sensor 1 according to the first exemplary embodiment is a structure of first acoustic matching layer 25.
  • first acoustic matching layer 25 is made porous by pressing and molding resin powders while heating.
  • a space not filled with the powders corresponds to voids 28 in first acoustic matching layer 25.
  • openings of voids 28 are formed from the powders disposed near an outermost surface, and voids 28 obviously have a part having an area equal to or larger than that of the opening at least one place.
  • liquid adhesive 3 is filled in voids 28 having such characteristics, case 3, first acoustic matching layer 25, and second acoustic matching layer 6 are superposed, and adhesive 3 that has wet and spread is solidified to achieve strong bonding and provide an ultrasonic sensor having excellent reliability.
  • metal powders can be pressurized and molded while heating.
  • a reference ultrasonic sensor was installed at a position 100 mm apart from the ultrasonic sensor to be evaluated in each example.
  • the ultrasonic waves emitted from the ultrasonic sensor to be evaluated in each example propagated to the reference sensor, and electromotive force generated in the reference sensor was used.
  • disc-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used as a piezoelectric element, and steel use stainless 304 (SUS304) having a thickness of 0.2 mm was used as a case. Further, only one acoustic matching layer was provided, and glass balloons were added to epoxy resin to have a density of 0.5 g/cm 3 and then have a thickness of 1.2 mm and a diameter of 10 mm.
  • the characteristics of the ultrasonic sensor used in each example can be recognized by the electromotive force generated from the reference ultrasonic sensor.
  • the ultrasonic sensor has excellent adhesive strength when the electromotive force after a thermal shock test is divided by the electromotive force before the thermal shock test, and an obtained value (sensitivity retention) is large.
  • the second exemplary embodiment shown in FIG. 2 was evaluated as follows.
  • piezoelectric element 2 disk-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used.
  • adhesive 3 an epoxy adhesive that is liquid at room temperature and solidifies by heating was used.
  • Case 4 including SUS304 having a thickness of 0.2 mm was used.
  • First acoustic matching layer 15 including PEEK resin having a thickness of 1 mm and a diameter of 10 mm was used.
  • Through-holes having a diameter of 300 pm at the openings on the surface facing case 4 and having a diameter of 400 pm at the openings on the surface facing second acoustic matching layer 6 were molded as voids 8.
  • a distance between the holes was 100 pm on a side where the diameter of the openings was 400 pm.
  • a polymethacrylimide resin foamed into a molded product of closed cells, having density of 0.07 g/cm 3 , and processed into a disk shape having a thickness of 0.8 mm and a diameter of 10 mm was used.
  • Ultrasonic sensor 11 was assembled as follows. First, first acoustic matching layer 15 was immersed in adhesive 3 at room temperature, case 4, first acoustic matching layer 15, and second acoustic matching layer 6 were disposed in order from below, and a load of 100 g was applied from above second acoustic matching layer 6. In this state, adhesive 3 wet and spread between first acoustic matching layer 15 and case 4 and between first acoustic matching layer 15 and second acoustic matching layer 6.
  • case 4 and piezoelectric element 2 were bonded by conductive adhesive, case 4 and electrode 7b were bonded by solder, and piezoelectric element 2 and electrode 7a were bonded by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 98 mV. Therefore, the sensitivity retention of the ultrasonic sensor was 98%.
  • the second exemplary embodiment shown in FIG. 2 was evaluated as follows.
  • piezoelectric element 2 disk-shaped lead zirconate titanate having a thickness of 3.8 mm and a diameter of 10 mm was used.
  • adhesive 3 an epoxy adhesive that is liquid at room temperature and solidifies by heating was used.
  • Case 4 including SUS304 having a thickness of 0.2 mm was used.
  • a polymethacrylimide resin foamed into a molded product of closed cells, having density of 0.07 g/cm 3 , and processed into a disk shape having a thickness of 0.8 mm and a diameter of 10 mm was used.
  • Ultrasonic sensor 11 was assembled as follows. First, first acoustic matching layer 15 was immersed in adhesive 3 at room temperature, case 4, first acoustic matching layer 15, and second acoustic matching layer 6 were disposed in order from below, and a load of 100 g was applied from above second acoustic matching layer 6. In this state, adhesive 3 wet and spread between first acoustic matching layer 15 and case 4 and between first acoustic matching layer 15 and second acoustic matching layer 6.
  • case 4 and piezoelectric element 2 were bonded by conductive adhesive
  • case 4 and electrode 7b were bonded by solder
  • piezoelectric element 2 and electrode 7a were bonded by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 98 mV. Therefore, the sensitivity retention of the ultrasonic sensor was 98%.
  • the second exemplary embodiment shown in FIG. 2 was evaluated as follows.
  • piezoelectric element 2 disk-shaped lead zirconate titanate having a thickness of 2.8 mm and a diameter of 10 mm was used.
  • adhesive 3 an epoxy adhesive that is liquid at room temperature and solidifies by heating was used.
  • Case 4 including SUS304 having a thickness of 0.2 mm was used.
  • a polymethacrylimide resin foamed into a molded product of closed cells, having a density of 0.07 g/cm 3 , and processed into a disk shape having a thickness of 0.8 mm and a diameter of 10 mm was used.
  • Ultrasonic sensor 11 was assembled as follows. First, first acoustic matching layer 15 was immersed in adhesive 3 at room temperature, case 4, first acoustic matching layer 5, and second acoustic matching layer 6 were disposed in order from below, and a load of 100 g was applied from above second acoustic matching layer 6. In this state, adhesive 3 wet and spread between first acoustic matching layer 15 and case 4 and between first acoustic matching layer 15 and second acoustic matching layer 6.
  • case 4 and piezoelectric element 2 were bonded by conductive adhesive, case 4 and electrode 7a were bonded by solder, and piezoelectric element 2 and electrode 7b were bonded by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 95 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 95 mV. Therefore, the sensitivity retention of the ultrasonic sensor was 100%.
  • the electromotive force of the ultrasonic sensor was a little smaller value than that in the second example, but was considered to be almost equivalent to the second example.
  • the average density of the first acoustic matching layer was about 1.2 which was an average of the density of the PEEK resin having a density of 1.3 g/cm 3 and the epoxy resin having a density of 1.0 g/cm 3
  • the average density of the first acoustic matching layer was as large as about 1.6 g/cm 3 .
  • the sensitivity retention ratio was 100%, which was further improved as compared with the second example. This can be inferred from a decrease in the shearing force in the thermal shock test because the difference in the thermal expansion coefficients between aluminum and the case including SUS304 is smaller than that between the PEEK resin and the case.
  • the third exemplary embodiment shown in FIG. 4 was evaluated as follows.
  • piezoelectric element 2 disk-shaped lead zirconate titanate having a thickness of 2.8 mm and a diameter of 10 mm was used.
  • adhesive 3 an epoxy adhesive that is liquid at room temperature and solidifies by heating was used.
  • Case 4 including SUS304 having a thickness of 0.2 mm was used.
  • first acoustic matching layer 25 PEEK resin was crushed and powders having an average particle size of 100 pm were heated to be molded into a thickness of 1 mm and a diameter of 10 mm.
  • Ultrasonic sensor 21 was assembled as follows. First, first acoustic matching layer 25 was immersed in adhesive 3 at room temperature, case 4, first acoustic matching layer 25, and second acoustic matching layer 6 were disposed in order from below, and a load of 100 g was applied from above second acoustic matching layer 6. In this state, adhesive 3 wet and spread between first acoustic matching layer 25 and case 4 and between first acoustic matching layer 25 and second acoustic matching layer 6.
  • case 4 and piezoelectric element 2 were bonded by conductive adhesive, case 4 and electrode 7a were bonded by solder, and piezoelectric element 2 and electrode 7b were bonded by solder.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 85 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 85 mV. Therefore, the sensitivity retention of the ultrasonic sensor was 100%.
  • the electromotive force was slightly smaller than those in the first to third exemplary embodiments.
  • a conceivable reason is that the first acoustic matching layer has a structure in which porous material including PEEK resin and the voids are filled with epoxy resin, and the acoustic impedance is similar when the ultrasonic waves propagate, but the ultrasonic waves repeatedly slightly reflect, which slightly reduces the efficiency.
  • the sensitivity retention is improved as compared with the second example.
  • the PEEK resin as a part of the first acoustic matching layer faces the case and is slightly affected by the shearing force due to the thermal shock, but in the fourth example, the particulate PEEK resin faces the case in a point contact form, that is, the adhesive of which approximately entire surface includes epoxy resin faces the case.
  • an ultrasonic sensor was manufactured by bonding the surface of openings 8a of voids 8 each having a diameter of 400 pm to face the case, and the ultrasonic sensor was evaluated.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 60 mV. Thus, the sensitivity retention of the ultrasonic sensor was 60%.
  • the electromotive force of the ultrasonic sensor after the manufacture was found to be equivalent to that in the first example.
  • the sensitivity retention was found to be lower than that in the first example.
  • a conceivable reason is that when linear elastic force generated in the case and the first acoustic matching layer is applied by the thermal shock test, a component of force in a direction perpendicular to a surface direction and away from the adhesive is generated in the adhesive in the voids in the first acoustic matching layer, and the first acoustic matching layer is likely to be peeled off.
  • an ultrasonic sensor was manufactured without providing through-holes, that is, voids in the first acoustic matching layer.
  • the electromotive force of the ultrasonic sensor manufactured as described above was 100 mV, and the electromotive force of the ultrasonic sensor after the thermal shock test was 20 mV. Thus, the sensitivity retention of the ultrasonic sensor was 20%.
  • the case and the acoustic matching layer were easily peeled off. Furthermore, almost all the adhesive remained on the case after peeling. This can be inferred from a deterioration of bonding on a PEEK resin interface because of the shearing force generated in the thermal shock test due to the thermal expansion coefficients of the case and the first matching layer.
  • the ultrasonic sensor when the acoustic matching layer is bonded to a material having a large difference in the thermal expansion coefficient, voids having a part of an area equivalent to or larger than that of the openings of the acoustic matching layer exist, and thus the ultrasonic sensor can be obtained that has excellent adhesive strength due to the anchor effect of the adhesive and can improve the environmental durability.
  • an ultrasonic sensor in a first disclosure includes a piezoelectric element, a first acoustic matching layer adhered to the piezoelectric element, and an adhesive that adheres the first acoustic matching layer to the piezoelectric element, in which the first acoustic matching layer has an opening on a surface adhered to the piezoelectric element and a void that communicates with the opening, and the adhesive is filled in the void.
  • the ultrasonic sensor in the first disclosure can obtain an anchor effect and excellent durability by integrating the adhesive that adheres the piezoelectric element and the first acoustic matching layer and the adhesive that solidifies in the void.
  • the ultrasonic waves need to be propagated from the piezoelectric element to a gas with high efficiency.
  • the ultrasonic waves need to be propagated from the first acoustic matching layer to the second acoustic matching layer and from the second acoustic matching layer to the gas with high efficiency.
  • a characteristic required for the first acoustic matching layer in addition to an acoustic impedance characteristic represented by equation (1), it is necessary to suppress an energy loss due to a deformation of the first acoustic matching layer (high propagation characteristics).
  • a substance with high propagation characteristics is hard (high elasticity).
  • a substance satisfying equation (1) and having high elasticity is a super engineering plastic such as PEEK in most cases.
  • the first acoustic matching layer has the opening facing the piezoelectric element or a member bonded to the piezoelectric element, and the adhesive that is cured after filling the void is bonded to the acoustic matching layer by chemical bonding and a mechanical bonding, that is, the anchor effect.
  • the adhesion is poor (bonding by a chemical bond is weak)
  • strong bonding is secured.
  • a facing surface of the adhesive is relatively easily bonded to ceramics or metals.
  • the piezoelectric element and the first acoustic matching layer which are firmly bonded, are not easily peeled off even when stress due to a difference in the thermal expansion coefficient occurs, and the ultrasonic sensor having excellent durability can be provided.
  • the ultrasonic sensor in a second disclosure includes a metal member having a flat plate, a piezoelectric element bonded to a first surface of the flat plate, and a first acoustic matching layer adhered to a second surface of the flat plate, and an adhesive that adheres the first acoustic matching layer to the flat plate.
  • the first acoustic matching layer has an opening on a surface adhered to the flat plate, and a void that communicates with the opening, and the adhesive is filled in the void.
  • the ultrasonic sensor in the second disclosure can obtain an anchor effect and excellent durability by integrating the adhesive that adheres the piezoelectric element bonded to the flat plate and the first acoustic matching layer and the adhesive that solidifies in the void.
  • an area of the opening on the surface may be smaller than or equal to a sectional area of the void.
  • An ultrasonic sensor in a fourth disclosure in any one of the first to third disclosures, may include a second acoustic matching layer adhered to the first acoustic matching layer with the adhesive, in which the void has an opening that communicates with the second acoustic matching layer.
  • the first acoustic matching layer may be at least partially resin.
  • a substance having a void that is filled with a liquid adhesive and solidified has density that is average density of the substance obtained from an existence ratio.
  • the acoustic matching layer includes two layers of the first acoustic matching layer facing the piezoelectric element and the second acoustic matching layer laminated on the first acoustic matching layer
  • the density of the second acoustic matching layer is about 0.05 g/cm 3
  • the density of the first acoustic matching layer (the acoustic impedance is highly dependent on the density because an acoustic velocity is less dependent on resin) is about 1 g/cm 3 in accordance with equation (1).
  • density of the adhesive such as epoxy adhesive is about 1 g/cm 3 .
  • the average density when the void is filled with an adhesive having density of about 1 g/cm 3 is also about 1 g/cm 3 .
  • the acoustic matching layer including a resin makes it possible to provide the ultrasonic sensor having excellent characteristics.
  • the first acoustic matching layer may be at least partially an inorganic substance or a metal.
  • an ultrasonic sensor having excellent heat resistance can be provided by using a brazing material or the like including an alloy as an adhesive.
  • the void may at least partially have a substantially cylindrical shape.
  • the acoustic matching layer partially having a substantially cylindrical shape is suitable for production.
  • the through-hole between the surface of the acoustic matching layer facing the piezoelectric element or the member bonded to the piezoelectric element and the surface not facing the piezoelectric element or the member corresponds to this void.
  • Such a shape can be produced, for example, by injection molding or by forming a through-hole in a plate-shaped member by machining when the acoustic matching layer is a thermoplastic resin.
  • the through-hole can be formed by die casting or by machining a plate-shaped member.
  • the stress due to the difference in the thermal expansion coefficients between the acoustic matching layer and the piezoelectric element or the member bonded to the piezoelectric element is applied schematically perpendicularly to the adhesive in the void.
  • the effect of suppressing a defect occurring at these interfaces is sufficient.
  • the void may be at least partially obtained by molding powder.
  • a member obtained by molding powder has the void having a larger area than that of the opening.
  • substances that can be molded in this way such as inorganic substances, metals, and resins. Therefore, the acoustic matching layer having appropriate physical properties such as density, an elastic modulus, and heat resistant temperature can be formed, and an ultrasonic sensor having excellent characteristics can be provided.
  • the adhesive in any one of the first to eighth disclosures, may have average density during curing of equal to or more than 0.8 g/cm 3 and less than or equal to 1.5 g/cm 3 .
  • the density of the first acoustic matching layer (the acoustic impedance is highly dependent on the density because an acoustic velocity is less dependent on resin) is about 1 g/cm 3 in accordance with equation (1).
  • This density corresponds to density of general resins.
  • density of the adhesive such as epoxy adhesive is about 1 g/cm 3 .
  • the average density when the void is filled with an adhesive having density of about 1 g/cm 3 is also about 1 g/cm 3 .
  • density of the first acoustic matching layer at which a maximum efficiency as an ultrasonic sensor can be obtained is different between a case where the density of the second acoustic matching layer is more than 0.05 g/cm 3 and a case where the density of the second acoustic matching layer is less than 0.05 g/cm 3 .
  • the density of the first acoustic matching layer being approximately equal to or more than about 0.8 g/cm 3 and less than or equal to about 1.5 g/cm 3 is optimal.
  • the adhesive in any one of the first to ninth disclosures, may be filled in the void in a liquid state and then cured to bond.
  • the liquid adhesive corresponding to at least a difference between the coating amount and the total volume of the void is left on the surface of the acoustic matching layer.
  • the acoustic matching layer is brought into contact with the piezoelectric element or the member bonded to the piezoelectric element in such a state, the liquid adhesive wets and spreads on the interface.
  • the piezoelectric element or the member bonded to the piezoelectric element which includes an inorganic substance or metal, is relatively easily bonded. Therefore, when solidified, the liquid adhesive is bonded to the piezoelectric element or the member bonded to the piezoelectric element by bonding force that is mainly a chemical bond, and the liquid adhesive is bonded to the acoustic matching layer by bonding force that is mainly an anchor effect. Due to a series of these effects, the piezoelectric element or the member bonded to the piezoelectric element and the acoustic matching layer are firmly bonded, and an ultrasonic sensor having excellent reliability can be provided.
  • the ultrasonic sensor of the present invention is suitable for use in flow rate meters for measuring various fluids.
  • the ultrasonic sensor of the present invention is preferably used in applications where use environment requires high durability in higher temperature or lower temperature environment than room temperature.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)
EP19826265.1A 2018-06-25 2019-06-17 Capteur à ultrasons Withdrawn EP3813385A4 (fr)

Applications Claiming Priority (2)

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JP2018119903A JP2020005027A (ja) 2018-06-25 2018-06-25 超音波センサー
PCT/JP2019/023823 WO2020004097A1 (fr) 2018-06-25 2019-06-17 Capteur à ultrasons

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KR102371895B1 (ko) * 2021-09-14 2022-03-07 오순옥 앵커 인장력 측정장치 및 이를 이용한 앵커 인장력 측정방법
CN115097014A (zh) * 2022-06-21 2022-09-23 辽宁机电职业技术学院 一种用于薄板无损检测的超声波装置

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JPS60235600A (ja) * 1984-05-08 1985-11-22 Shimadzu Corp 超音波探触子とその製造方法
JP3488102B2 (ja) 1998-11-06 2004-01-19 オリンパス株式会社 超音波探触子
JP4400004B2 (ja) * 2001-04-25 2010-01-20 パナソニック株式会社 超音波送受波器
EP1416255A1 (fr) * 2002-01-28 2004-05-06 Matsushita Electric Industrial Co., Ltd. Emetteur-recepteur ultrasonore et debitmetre ultrasonore
US6788620B2 (en) * 2002-05-15 2004-09-07 Matsushita Electric Ind Co Ltd Acoustic matching member, ultrasound transducer, ultrasonic flowmeter and method for manufacturing the same
JP2004343263A (ja) * 2003-05-14 2004-12-02 Matsushita Electric Ind Co Ltd 音響整合部材およびその製造方法
JP2004343658A (ja) * 2003-05-19 2004-12-02 Matsushita Electric Ind Co Ltd 超音波送受波器とその製造方法及びそれを用いた超音波流量計
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JP4701059B2 (ja) 2005-10-04 2011-06-15 東光東芝メーターシステムズ株式会社 超音波センサ及びその製造方法ならびにその最適設計装置
JP4777198B2 (ja) * 2006-09-11 2011-09-21 愛知時計電機株式会社 超音波センサ
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JP2017163330A (ja) * 2016-03-09 2017-09-14 セイコーエプソン株式会社 超音波デバイス、超音波モジュール、及び超音波測定装置

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JP2020005027A (ja) 2020-01-09
EP3813385A4 (fr) 2021-07-28
CN112313968A (zh) 2021-02-02
US20210208111A1 (en) 2021-07-08
WO2020004097A1 (fr) 2020-01-02

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